Exhaust Pressure Results 4.8L/76mm

Foose04 · 09-28-2012, 02:56 AM

Figured I'd share this over here in case some new guys comes in here looking put a snail on his cheby.

Going to copy and paste my post I made on PT.Net because i'm lazy and thats what lazy guys do.

Well i've had the itch to do this test so I finally stepped and knocked it out. I did the best I could so I hope it's useful to others in picking out the proper turbo for their setup.

Before I go on, I want to first say I'm very happy with what I have done performance wise with my Magnum turbo. That said, i'm just has happy to remove it for something better suited for my application.

I made a video showing the tonights testing with Go-Pro mounted on gauges. It did pretty well, but it was night time so it is what it is.

My test setup had a pressure drop of 4-5 psi at 50psi. This is likely from the 10 feet of hose required from cross-over pipe to pillar. Posted results in video did not include correction but I WILL include it in the posted numbers for those who don't watch the clip.

Test sample was from 3 runs that all had close to identical feedback. I can't confirm RPM, but all pulls was above 3500 before going to WOT and ending slighty above 6000.

From the camera on Average (corrected):

5 PSI Boost = 17 PSI Exhaust
10PSI Boost = 29 PSI Exhaust
15PSI Boost = 41 PSI Exhaust
18PSI Boost = 54 PSI Exhaust
21PSI Boost = 55 PSI Exhaust

Notice a nearly 3-1 Exh/Boost ratio from start to finish.

I then tested a 65 Wet shot, I turned boost down to counter boost spike to maintain a max of 21psi. Results showed little no gain in back pressure on the smaller nitrous shot that was triggered at 4000RPMS.

Conclusion, my truck never really picked up MPH at the track above 16-17PSI. Even at 20-21psi, MPH was nearly identical supporting the turbine wheel is past it's efficiency. I had to install a stiffer wastegate spring to make 18+psi possible, but this is a bad choice with this turbo.

While the BP seems high, i've read a lot of factory cars have BP of 2.5-3/1 for fast response and street manners. So this isn't horrible, but it is on the high side for a gear head looking for power.

In my "opinion". If your looking to make MAX power on this turbo on a 4.8L, keep it at or below 15psi with a upgraded cam engine. On a 5.3L, expect it to be a few PSI lower, 6.0 even lower.

Happy Boostin guys!! I will run the same test on my new BL475R within the next few weeks.

Video of testing, recommend watching in 720HD to see gauges:

1997b4c · 09-28-2012, 07:16 AM

That's a lot of back pressure keeps a lot of heat trapped

GreebeanZ28 · 09-28-2012, 08:09 AM

Yep, time for some bullhorns.

ForceFed4g63 · 09-28-2012, 08:30 AM

Good tests Rob, thanks for posting it up. I want to do either a turbo 4.8 or 5.3 in the fox so this helps!

Foose04 · 09-28-2012, 01:47 PM

Quote:

Originally Posted by 1997b4c

That's a lot of back pressure keeps a lot of heat trapped

Yeah I wouldn't think the exhaust valve is a big fan of opening to 55PSi of exhaust wanting back in the engine.

Quote:

Originally Posted by GreebeanZ28

Yep, time for some bullhorns.

If has another 1000HP I'd have horns all over this truck.

Quote:

Originally Posted by ForceFed4g63

Good tests Rob, thanks for posting it up. I want to do either a turbo 4.8 or 5.3 in the fox so this helps!

I bet this BW turbo is going to be about right man. We'll see though.

454rat · 09-28-2012, 02:11 PM

Get a job! well done on the trouble shooting, its interesting to know how the pieces work and effect each other. some of the factors would also obviously include exhaust size and type for back pressure.

Foose04 · 09-28-2012, 02:23 PM

Hey it's my weekend! Yeah just wanted some before and after data. I knew it was high, but didn't expect 3 to 1 as early as 5psi. The exhaust down-stream is also getting redone. Hows the Red Dragon?

ForceFed4g63 · 09-28-2012, 02:43 PM

What's the diameter of your exhaust?

Foose04 · 09-28-2012, 04:44 PM

3" with a cutout mid truck.

ForceFed4g63 · 09-28-2012, 04:53 PM

I bet you would benefit hugely from making it at least 4"

RoadconeTuning · 09-30-2012, 10:25 AM

thats way high...

Foose04 · 10-03-2012, 12:38 AM

Update shots on the swap. She sure is purrrdy... Waiting on DP/Intake/cat-back tubing. Can't wait, this rig should roll out.

bwelch · 10-03-2012, 01:04 AM

6.3x here you come...

TurboWS6 · 10-03-2012, 01:12 AM

Sweet.

ForceFed4g63 · 10-03-2012, 09:03 AM

Very nice, switching to twin scroll should help a bit too!

RoadconeTuning · 10-03-2012, 09:09 AM

twin scroll wont make a bit of a difference if he doesnt have the hot side setup for it...

BAD BOB · 10-03-2012, 09:17 AM

Quote:

Originally Posted by RoadconeTuning

twin scroll wont make a bit of a difference if he doesnt have the hot side setup for it...

but will work just fine on a open flange

RoadconeTuning · 10-03-2012, 11:30 AM

yup, the 7M-GTE powered supra and 3S-GTE MR2's both have a CT26 turbo... the MR2 turbo is twin scroll and kills about 15hp up top due to restriction tho.

Darryl Buckner · 10-03-2012, 11:41 AM

Bob needs to hook you up with a side exit exhaust in the front fender, that should drop a little back pressure..

Foose04 · 10-03-2012, 04:17 PM

Quote:

Originally Posted by bwelch

6.3x here you come...

I dig your style Sir!

Quote:

Originally Posted by Darryl Buckner

Bob needs to hook you up with a side exit exhaust in the front fender, that should drop a little back pressure..

Roberts crazy enough to do it.. I said man this 4"going to be a tight fit. "Robert, no I'd do 5" if it was mine." Lol

09-28-2012, 02:56 AM	#1
Foose04 Senior Member Join Date: Feb 2010 Posts: 965	Exhaust Pressure Results 4.8L/76mm Figured I'd share this over here in case some new guys comes in here looking put a snail on his cheby. Going to copy and paste my post I made on PT.Net because i'm lazy and thats what lazy guys do. Well i've had the itch to do this test so I finally stepped and knocked it out. I did the best I could so I hope it's useful to others in picking out the proper turbo for their setup. Before I go on, I want to first say I'm very happy with what I have done performance wise with my Magnum turbo. That said, i'm just has happy to remove it for something better suited for my application. I made a video showing the tonights testing with Go-Pro mounted on gauges. It did pretty well, but it was night time so it is what it is. My test setup had a pressure drop of 4-5 psi at 50psi. This is likely from the 10 feet of hose required from cross-over pipe to pillar. Posted results in video did not include correction but I WILL include it in the posted numbers for those who don't watch the clip. Test sample was from 3 runs that all had close to identical feedback. I can't confirm RPM, but all pulls was above 3500 before going to WOT and ending slighty above 6000. From the camera on Average (corrected): 5 PSI Boost = 17 PSI Exhaust 10PSI Boost = 29 PSI Exhaust 15PSI Boost = 41 PSI Exhaust 18PSI Boost = 54 PSI Exhaust 21PSI Boost = 55 PSI Exhaust Notice a nearly 3-1 Exh/Boost ratio from start to finish. I then tested a 65 Wet shot, I turned boost down to counter boost spike to maintain a max of 21psi. Results showed little no gain in back pressure on the smaller nitrous shot that was triggered at 4000RPMS. Conclusion, my truck never really picked up MPH at the track above 16-17PSI. Even at 20-21psi, MPH was nearly identical supporting the turbine wheel is past it's efficiency. I had to install a stiffer wastegate spring to make 18+psi possible, but this is a bad choice with this turbo. While the BP seems high, i've read a lot of factory cars have BP of 2.5-3/1 for fast response and street manners. So this isn't horrible, but it is on the high side for a gear head looking for power. In my "opinion". If your looking to make MAX power on this turbo on a 4.8L, keep it at or below 15psi with a upgraded cam engine. On a 5.3L, expect it to be a few PSI lower, 6.0 even lower. Happy Boostin guys!! I will run the same test on my new BL475R within the next few weeks. Video of testing, recommend watching in 720HD to see gauges: __________________ 12 GMC Denali HD: 4x4, 12" Bullet Proof, 24x12 American Forces, 40x15.50 Toyo M/T's, h&s mini max, deleted, 5" axle dump, S&B intake,tractions bars, air bags. 04 GMC 1500RST: TMS Iron 347/S480/4l80E - 9.63@143.22 05 GMC 2500HD: LLY@372HP/669TQ, 4x4, 8" FabTech, 4.56 gears & 37" Toyo M/T's Last edited by Foose04; 09-28-2012 at 04:53 AM.

09-28-2012, 08:09 AM	#3
GreebeanZ28 Senior Member Join Date: Oct 2011 Location: Easley Posts: 2,300	Yep, time for some bullhorns. __________________

09-28-2012, 08:30 AM	#4
ForceFed4g63 Senior Member Join Date: Oct 2009 Location: Aiken Posts: 7,002	Good tests Rob, thanks for posting it up. I want to do either a turbo 4.8 or 5.3 in the fox so this helps! __________________ 2000 WS6 2005 CTS-V 2004 Titan QC 4x4

09-28-2012, 02:11 PM	#6
454rat Senior Member Join Date: Nov 2011 Posts: 97	Get a job! well done on the trouble shooting, its interesting to know how the pieces work and effect each other. some of the factors would also obviously include exhaust size and type for back pressure. __________________ 78 Malibu E-85 bbc 68 Chevelle

09-28-2012, 02:23 PM	#7
Foose04 Senior Member Join Date: Feb 2010 Posts: 965	Hey it's my weekend! Yeah just wanted some before and after data. I knew it was high, but didn't expect 3 to 1 as early as 5psi. The exhaust down-stream is also getting redone. Hows the Red Dragon? __________________ 12 GMC Denali HD: 4x4, 12" Bullet Proof, 24x12 American Forces, 40x15.50 Toyo M/T's, h&s mini max, deleted, 5" axle dump, S&B intake,tractions bars, air bags. 04 GMC 1500RST: TMS Iron 347/S480/4l80E - 9.63@143.22 05 GMC 2500HD: LLY@372HP/669TQ, 4x4, 8" FabTech, 4.56 gears & 37" Toyo M/T's

09-28-2012, 07:16 AM	#2
1997b4c Senior Member Join Date: Jul 2011 Posts: 343	That's a lot of back pressure keeps a lot of heat trapped

09-28-2012, 02:43 PM	#8
ForceFed4g63 Senior Member Join Date: Oct 2009 Location: Aiken Posts: 7,002	What's the diameter of your exhaust? __________________ 2000 WS6 2005 CTS-V 2004 Titan QC 4x4

09-28-2012, 04:44 PM	#9
Foose04 Senior Member Join Date: Feb 2010 Posts: 965	3" with a cutout mid truck. __________________ 12 GMC Denali HD: 4x4, 12" Bullet Proof, 24x12 American Forces, 40x15.50 Toyo M/T's, h&s mini max, deleted, 5" axle dump, S&B intake,tractions bars, air bags. 04 GMC 1500RST: TMS Iron 347/S480/4l80E - 9.63@143.22 05 GMC 2500HD: LLY@372HP/669TQ, 4x4, 8" FabTech, 4.56 gears & 37" Toyo M/T's

09-28-2012, 04:53 PM	#10
ForceFed4g63 Senior Member Join Date: Oct 2009 Location: Aiken Posts: 7,002	I bet you would benefit hugely from making it at least 4" __________________ 2000 WS6 2005 CTS-V 2004 Titan QC 4x4

09-30-2012, 10:25 AM	#11
RoadconeTuning Senior Member Join Date: Jun 2008 Location: Upstate, SC Posts: 2,684	thats way high... __________________ FIRSBIRZ

10-03-2012, 12:38 AM	#12
Foose04 Senior Member Join Date: Feb 2010 Posts: 965	Update shots on the swap. She sure is purrrdy... Waiting on DP/Intake/cat-back tubing. Can't wait, this rig should roll out. __________________ 12 GMC Denali HD: 4x4, 12" Bullet Proof, 24x12 American Forces, 40x15.50 Toyo M/T's, h&s mini max, deleted, 5" axle dump, S&B intake,tractions bars, air bags. 04 GMC 1500RST: TMS Iron 347/S480/4l80E - 9.63@143.22 05 GMC 2500HD: LLY@372HP/669TQ, 4x4, 8" FabTech, 4.56 gears & 37" Toyo M/T's

10-03-2012, 01:04 AM	#13
bwelch Senior Member Join Date: Aug 2009 Posts: 3,774	6.3x here you come... __________________

10-03-2012, 01:12 AM	#14
TurboWS6 Senior Member Join Date: Jan 2012 Location: Rockingham, NC Posts: 799	Sweet. __________________ [IMG][/IMG] 1999 WS6, 6.0L, S480, TH400, Dana 60 1967 GTO 496" Poncho stroker, 4 speed, 4:11s 2007 Hemi Ram 2013 Grand Caravan RT 1997 Civic

10-03-2012, 09:03 AM	#15
ForceFed4g63 Senior Member Join Date: Oct 2009 Location: Aiken Posts: 7,002	Very nice, switching to twin scroll should help a bit too! __________________ 2000 WS6 2005 CTS-V 2004 Titan QC 4x4

10-03-2012, 09:09 AM	#16
RoadconeTuning Senior Member Join Date: Jun 2008 Location: Upstate, SC Posts: 2,684	twin scroll wont make a bit of a difference if he doesnt have the hot side setup for it... __________________ FIRSBIRZ

10-03-2012, 11:30 AM	#18
RoadconeTuning Senior Member Join Date: Jun 2008 Location: Upstate, SC Posts: 2,684	yup, the 7M-GTE powered supra and 3S-GTE MR2's both have a CT26 turbo... the MR2 turbo is twin scroll and kills about 15hp up top due to restriction tho. __________________ FIRSBIRZ

10-03-2012, 11:41 AM	#19
Darryl Buckner The Top Dog Join Date: Dec 2007 Posts: 2,318	Bob needs to hook you up with a side exit exhaust in the front fender, that should drop a little back pressure.. __________________ When the people fear the government, there is tyranny. When the government fears the people, there is liberty. Thomas Jefferson